Celestial dark stuff requires dark sky to record them. Lesson learned. I was a little bit too optimistic about my suburban conditions when I placed Iris nebula into the field of view of my imaging setup. And additionally there was some humidity and high clouds, so the stars are little bit bloated. Iris nebula itself is catalogued at LBN487 position of Lynds catalogue and as vdB 139 in van den Bergh catalogue. And NGC7023 is star open cluster inside. Iris is rather dust reflection nebula, so it shines in the color of the centre illuminating star SAO 19158. But not only reflection. There are also some red color areas in the nebula center. This hue comes partially from hydrogen alpha emission. But also from the broadband photoluminescence associated with dust particles by high energy UV radiation. This phenomena is called extended red emission (ERE). The bright area of Iris nebula is pretty large (about half of the apparent Moon diameter) and quite bright, but is not an easy visual target due to presence of bright central star. And this bright part is surrounded with dark dusty clouds, that I wanted to reveal, but as I wrote at the beginning – I was too optimistic about my suburban sky. Dark dusties around NGC7023 and Iris came out, but not in a way I hoped 🙂
Image below was made over three October nights using 130/910 refractor, QHY163M camera and EQ6 mount. It is total 8 hours of exposures through LRGB filters.